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Time course of deficits in finger use induced by muscimol injection into the first somatosensory cortex of awake monkeys
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THE PATTERN OF CORTICO-CORTICAL CONNECTION FROM THE FIRST SOHATOSENSORY AREA ( SI ) TO THE FIFTH
SOMATOSENSORY AREA (
SV )IN THE CAT. AKIO MORI*, YOSHIYUKI TSUBOI*,
NAOKI HANASHINA* AND
RHYUJI Sb741NO.Department of_f Physiology, Nihon University, School of Dentistry, 1-8-13 KandaSurugadal, Chiyoda-Ku, Tokyo 101, Japan. The physiological properties of neurons In SV and pattern of cortical projection from area 2 of SI to SV in cats were studied by using slngle-unit recording and collision techniques. Under Ketamine anesthesia ( 35mg/kg, i.p.) a double-barreled chamber was installed over the SV and area 2. Four stimulating mlcroelectrodes were then inserted into SV and a single recording mlcroelectrode was placed into area 2. The mlcroelectrodes (Stony type) were used to record antidromlc responses from area 2 following Intracortlcal mtcrostlmulatlon (ICMS) of the SV wlth 30uA or less, and also for recording unitary spikes from these areas. The receptive fields (RFs) of neurons in SV and area 2 were examined using natural stimulation such as air puffs delivered to the hair, light touch, and pressure on the surface of the body. The maJorlty of antldromlcally- identified neurons received somatotoplcally-organlzed afferent inputs from the skin or hair on the contralateral side of the body. Both the antidromlcally-activated area 2 and neurons around the stimulating electrode in SV were activated by sensory input from similar peripheral areas of the body. Results indicate that SV neurons have larger RFs than area 2. After ablation of the antldromlcally-actlvated area 2, spontaneous discharges of SV neurons were depressed. However thls did not change the size of RFs. Our findings suggest that the excitability of SV neurons is influenced through the cortlco-cortical projection from area 2 of SI to SV.
DISTRIBUTION OF 3H-MUS~IMOL INJECTED INTO MA~AQU~ SOMATOSENSORY CORTEX. YUK]O HIRATA L, MICHIO TANAKA ~ AND YOSHIAK| IWAMURA ~. ~Denartmeot of A~2L_t_~ Universit~ of th~ B j n k ~ s School o~ Medicine. 207 Uehara. Nishihar~, Okioaw~ 903Ol.~Departmest ~ Physioio~y. Toho U n i v e r s i t y School of Medicine. 5-21-16, Oomori-Nishi Qotak~ ~ 143 J a p a n . Th~ d i s t r i b u t i o n of JH-Muscimoi(2.7ng/0.5~l,18. SKBq) i n j e c t e d i n t o ] a y e r IV of m a c a q u e s o m a t o s e n s o r y c o r t e x was e x a m i n e d by a u t o r a d i o g r a p h y 20, 40, 60, 8 0 , and 100 m i n u t e s a f t e r the injection. The r a d i o a c t i v e area enlarged i n s i z e and c h a n g e d in s h a p e w i t h t h e l a p s e o f t i m e a f t e r the injection. The r a d i o a c t i v e z o n e was f i r s t (20 g i n ) o f s p i n d l e form with horizontal d i a m e t e r a b o u t Imm. By 40 min, t h e s h a p e o f t h e r a d i o a c t i v e area became approximately a barrel of d i a m e t e r a b o u t 2. Smm. 60 t o 80 w i n a f t e r injection i t b e c a m e a d i s c 3 t o 4 mm in d i a m e t e r . In e a r l i e r stages (20 t o 40 m i n ) , s i l v e r grains showed a center-to-periphery density gradient but later the grains were distributed rather uniformly throughout the positive cortical area. Throughout the course examined, the grains did not show either laminar specificity or any noticeable association with neuronal or glial cellular structures. This suggests that the injected muscimol extended through the cortical tissue n o t by a c t i v e transport in c o r t i c a l structures, but l i k e l y by d i f f u s i o n alone.
T I M E C O U R S E O F D E F I C I T S IN F I N G E R USE I N D U C E D BY M U S C I M O L I N J E C T I O N INTO T H E F I R S T SOMATOSENSORY CORTEX OF AWAKE MONKEYS. YOSHIAKI IWAMURA AND MICHIO TANAKA, D e p a r t m e n t of P h y s i o l o g y , T o h o U n i v e r s i t y S c h o o l of M e d i c i n e , O m o r i - N i s h i , Otaku, Tokyo, 143, J a p a n We a n a l y z e d the t i m e c o u r s e of b e h a v i o r a l d e f i c i t s in r e t r i e v a l of a p i e c e of a p p l e f r o m a small w e l l on a w o o d e n b o a r d a f t e r l o c a l i n j e c t i o n of m u s c i m o l (GABA a g o n i s t ) in the p o s t c e n t r a l g y r u s of a w a k e m o n k e y s . The m o n k e y ' s b e h a v i o r was d i s t u r b e d i m m e d i a t e l y a f t e r the m u s c i m o l i n j e c t i o n , but the d i s t u r b a n c e s w e r e o f t e n s u b t l e and w e r e q u i c k l y o v e r c o m e by m i n o r c h a n g e s in s t r a t e g y . In 2 0 - 4 0 m i n u t e s a f t e r the i n j e c t i o n , d e f i c i t s b e c a m e m o r e a n d m o r e a p p a r e n t . L a t e r t h a n 60 m i n u t e s a f t e r the i n j e c t i o n the a n i m a l c o u l d not r e t r i e v e b a i t by p r e c i s i o n g r i p at all, and a d o p t e d d i f f e r e n t s t r a t e g i e s such as d i g - a n d - g r a b or s c r a t c h - a n d - g r a b type m e t h o d s . D i f f e r e n t f r o m e a r l i e r s y m p t o m s , the late o n e s w e r e less s p e c i f i c to the i n j e c t i o n sites, and t h e y w e r e e x p r e s s i o n s of d r a s t i c a l l y a l t e r e d s t r a t e g i e s in the r e t r i e v a l of bait. The p r e c e d i n g a b s t r a c t d e s c r i b e d the t i m e c o u r s e of the s p r e a d of i n j e c t e d m u s c i m o l in c o r t i c a l g r a y m a t t e r . R e f e r r i n g to this data, we c o n c l u d e t h a t the m o n k e y can c o m p e n s a t e for the d e f i c i t s c a u s e d b y l o c a l i z e d d e p r i v a t i o n of s e n s o r y i n f o r m a t i o n w i t h o u t c h a n g i n g d r a s t i c a l l y the s t r a t e g y of p r e c i s i o n g r i p w h e n m u s c i m o l was l i m i t e d w i t h i n a c i r c u m s c r i b e d a r e a of 1 m m radius, a n d t h a t the p r e c i s i o n g r i p in the p r e s e n t t a s k r e l i e s on c o r t i c a l s t r u c t u r e s w i t h i n a r a d i u s of 2-3 mm.
THE PATTERN OF CORTICO-CORTICAL CONNECTION FROM THE FIRST SOHATOSENSORY AREA ( SI ) TO THE FIFTH
SOMATOSENSORY AREA (
SV )IN THE CAT. AKIO MORI*, YOSHIYUKI TSUBOI*,
NAOKI HANASHINA* AND
RHYUJI Sb741NO.Department of_f Physiology, Nihon University, School of Dentistry, 1-8-13 KandaSurugadal, Chiyoda-Ku, Tokyo 101, Japan. The physiological properties of neurons In SV and pattern of cortical projection from area 2 of SI to SV in cats were studied by using slngle-unit recording and collision techniques. Under Ketamine anesthesia ( 35mg/kg, i.p.) a double-barreled chamber was installed over the SV and area 2. Four stimulating mlcroelectrodes were then inserted into SV and a single recording mlcroelectrode was placed into area 2. The mlcroelectrodes (Stony type) were used to record antidromlc responses from area 2 following Intracortlcal mtcrostlmulatlon (ICMS) of the SV wlth 30uA or less, and also for recording unitary spikes from these areas. The receptive fields (RFs) of neurons in SV and area 2 were examined using natural stimulation such as air puffs delivered to the hair, light touch, and pressure on the surface of the body. The maJorlty of antldromlcally- identified neurons received somatotoplcally-organlzed afferent inputs from the skin or hair on the contralateral side of the body. Both the antidromlcally-activated area 2 and neurons around the stimulating electrode in SV were activated by sensory input from similar peripheral areas of the body. Results indicate that SV neurons have larger RFs than area 2. After ablation of the antldromlcally-actlvated area 2, spontaneous discharges of SV neurons were depressed. However thls did not change the size of RFs. Our findings suggest that the excitability of SV neurons is influenced through the cortlco-cortical projection from area 2 of SI to SV.
DISTRIBUTION OF 3H-MUS~IMOL INJECTED INTO MA~AQU~ SOMATOSENSORY CORTEX. YUK]O HIRATA L, MICHIO TANAKA ~ AND YOSHIAK| IWAMURA ~. ~Denartmeot of A~2L_t_~ Universit~ of th~ B j n k ~ s School o~ Medicine. 207 Uehara. Nishihar~, Okioaw~ 903Ol.~Departmest ~ Physioio~y. Toho U n i v e r s i t y School of Medicine. 5-21-16, Oomori-Nishi Qotak~ ~ 143 J a p a n . Th~ d i s t r i b u t i o n of JH-Muscimoi(2.7ng/0.5~l,18. SKBq) i n j e c t e d i n t o ] a y e r IV of m a c a q u e s o m a t o s e n s o r y c o r t e x was e x a m i n e d by a u t o r a d i o g r a p h y 20, 40, 60, 8 0 , and 100 m i n u t e s a f t e r the injection. The r a d i o a c t i v e area enlarged i n s i z e and c h a n g e d in s h a p e w i t h t h e l a p s e o f t i m e a f t e r the injection. The r a d i o a c t i v e z o n e was f i r s t (20 g i n ) o f s p i n d l e form with horizontal d i a m e t e r a b o u t Imm. By 40 min, t h e s h a p e o f t h e r a d i o a c t i v e area became approximately a barrel of d i a m e t e r a b o u t 2. Smm. 60 t o 80 w i n a f t e r injection i t b e c a m e a d i s c 3 t o 4 mm in d i a m e t e r . In e a r l i e r stages (20 t o 40 m i n ) , s i l v e r grains showed a center-to-periphery density gradient but later the grains were distributed rather uniformly throughout the positive cortical area. Throughout the course examined, the grains did not show either laminar specificity or any noticeable association with neuronal or glial cellular structures. This suggests that the injected muscimol extended through the cortical tissue n o t by a c t i v e transport in c o r t i c a l structures, but l i k e l y by d i f f u s i o n alone.
T I M E C O U R S E O F D E F I C I T S IN F I N G E R USE I N D U C E D BY M U S C I M O L I N J E C T I O N INTO T H E F I R S T SOMATOSENSORY CORTEX OF AWAKE MONKEYS. YOSHIAKI IWAMURA AND MICHIO TANAKA, D e p a r t m e n t of P h y s i o l o g y , T o h o U n i v e r s i t y S c h o o l of M e d i c i n e , O m o r i - N i s h i , Otaku, Tokyo, 143, J a p a n We a n a l y z e d the t i m e c o u r s e of b e h a v i o r a l d e f i c i t s in r e t r i e v a l of a p i e c e of a p p l e f r o m a small w e l l on a w o o d e n b o a r d a f t e r l o c a l i n j e c t i o n of m u s c i m o l (GABA a g o n i s t ) in the p o s t c e n t r a l g y r u s of a w a k e m o n k e y s . The m o n k e y ' s b e h a v i o r was d i s t u r b e d i m m e d i a t e l y a f t e r the m u s c i m o l i n j e c t i o n , but the d i s t u r b a n c e s w e r e o f t e n s u b t l e and w e r e q u i c k l y o v e r c o m e by m i n o r c h a n g e s in s t r a t e g y . In 2 0 - 4 0 m i n u t e s a f t e r the i n j e c t i o n , d e f i c i t s b e c a m e m o r e a n d m o r e a p p a r e n t . L a t e r t h a n 60 m i n u t e s a f t e r the i n j e c t i o n the a n i m a l c o u l d not r e t r i e v e b a i t by p r e c i s i o n g r i p at all, and a d o p t e d d i f f e r e n t s t r a t e g i e s such as d i g - a n d - g r a b or s c r a t c h - a n d - g r a b type m e t h o d s . D i f f e r e n t f r o m e a r l i e r s y m p t o m s , the late o n e s w e r e less s p e c i f i c to the i n j e c t i o n sites, and t h e y w e r e e x p r e s s i o n s of d r a s t i c a l l y a l t e r e d s t r a t e g i e s in the r e t r i e v a l of bait. The p r e c e d i n g a b s t r a c t d e s c r i b e d the t i m e c o u r s e of the s p r e a d of i n j e c t e d m u s c i m o l in c o r t i c a l g r a y m a t t e r . R e f e r r i n g to this data, we c o n c l u d e t h a t the m o n k e y can c o m p e n s a t e for the d e f i c i t s c a u s e d b y l o c a l i z e d d e p r i v a t i o n of s e n s o r y i n f o r m a t i o n w i t h o u t c h a n g i n g d r a s t i c a l l y the s t r a t e g y of p r e c i s i o n g r i p w h e n m u s c i m o l was l i m i t e d w i t h i n a c i r c u m s c r i b e d a r e a of 1 m m radius, a n d t h a t the p r e c i s i o n g r i p in the p r e s e n t t a s k r e l i e s on c o r t i c a l s t r u c t u r e s w i t h i n a r a d i u s of 2-3 mm.